Abstract : Surveys of 2,670 patients with acute diarrhea and 1,500 normal, healthy individuals in Bangkok, Thailand, indicate that enteropathogenic Escherichia coli are significant in diarrheal diseases of infants in that country. During the 16 months of this study, approximately 10 per cent of the diarrhea in children under 2 years of age was due to these organisms. Serotypes 025:B19:B23, 0119:B14 and 0128:B12 were the most frequently found strains both in patients and in symptomless individuals. Serotypes 0111:B4 and 055:B5, among the most common serotypes in many parts of the world, were encountered rarely. Of 183 E. coli isolated from patients, 055:B5 was cultured 5 times and 0111:B4 was found in a single instance. Neither was obtained from normal, healthy subjects. (Author)